The backstay on my boat is the "inverted Y" type of backstay with a 6 to 1 block and tackle on one leg of the Y (giving what I think is an approximate 12 to 1 mechanical advantage overall). The rig is a 9/10 fractional rig with only one lower shroud
(each side), with swept back spreaders and a roller furling genoa
. The wire sizes are 7/16" for the backstay, and 1/2" for the shrouds (lower and cap) and 5/16" for the intermediates (total of 2 spreaders). It is a production cruiser type of boat (sloop rig). I can't seem to find a loos guage for determining tension that will accept wire this thick?
The information from Selden on this rig, is that the backstay should not be tensioned more than 20% of it's breaking strength (at any time), and that it should never be allowed to completely slacken.
My questions are:
How do I tell what level of adjustment to use? When do I use the full 20% tension and how do I tell when I am there? For downwind, how much do I "let it off"? In light wind
, how much do I let it off?
For example to loosen for downwind, do I let 3" of line through the 6 to 1, or ??? from the fully tensioned position?
Up to now, I have avoided using the backstay adjustor, probably because I am unsure of how to set it properly.
Thanks in advance for your advise and help in "demystifying" this control,